When completing a horizontal or other high deviation well, several zones of interest are typically completed per horizontal or highly deviated lateral, even though at least some of these zones lie within a single geological formation. A horizontal lateral, for example, can desirably be divided into isolatable longitudinal segments which correspond to substantially separate, naturally fractured regions existing in the subterranean formation through which the horizontal lateral extends. Additionally, a horizontal lateral can be divided into isolatable longitudinal segments in order to separate producing regions from shale streaks or other natural obstructions extending into the formation.
Several advantages can be obtained by dividing a horizontal or other highly deviated lateral into separate isolatable segments wherein each segment is associated with a different zone of interest. For example, by dividing a well lateral in this manner, stimulation treatments can be individually and separately directed to specific zones of interest. Consequently, such stimulation treatments can be conducted in a much more effective and efficient manner. Additionally, the division of a well lateral into separate isolatable segments (a) allows individual zones of interest to be selectively tapped for production, (b) allows nonproductive regions to be readily isolated from producing zones, and (c) allows gassed out and/or watered out zones to be quickly identified and isolated from zones which are producing substantially less gas and/or water.
U.S. Pat. No. 4,949,788 discloses a method of completing a horizontal well wherein a casing string including a plurality of casing valves is cemented in a wellbore. Each casing valve includes (a) an outer housing with a plurality of ports defined through the wall thereof and (b) a sliding sleeve received in the housing and including a plurality of sleeve ports. After the casing string is cemented in the formation, a fracturing tool including a casing valve positioner is run into the casing string. The casing valve positioner is operable for opening and closing the casing valves. Using the fracturing tool string, the formation is fractured by sequentially opening each of the casing valves and pumping a fracturing fluid therethrough. Following the fracturing procedure, a production tubing string is placed in the casing and is used to produce formation fluids from selected formation zones.
The completion method of U.S. Pat. No. 4,949,788 allows individual zones of interest to be selectively isolated and opened by operating the appropriate casing valves. However, even when supplemental fracturing or other stimulation procedures are used, completion methods of the type disclosed in U.S. Pat. No. 4,949,788 (i.e., methods wherein cement sheaths are placed across naturally producing formations) typically substantially reduce the production rates obtainable from the naturally producing formations.
U.S. Pat. No. 4,714,177 discloses a method for completing a horizontal well which utilizes a casing string composed of alternating casing valves and casing packers. When expanded in the wellbore, each of the casing packers forms a seal between the exterior of the casing string and the wellbore wall. Consequently, the casing packers operate to isolate discrete segments of the horizontal lateral to thereby allow localized production and remedial treatments.
Unfortunately, methods of the type described in U.S. Pat. No. 4,714,117 are somewhat unreliable. Casing packers can be easily damaged while the casing string is being run into the wellbore. Consequently, casing packer systems typically have undesirably high failure rates.
U.S. Pat. No. 4,972,906 discloses a method for treating a gravel packed vertical well wherein the entire lowermost portion of the vertical well is plugged. The method of U.S. Pat. No. 4,972,906 is particularly applicable for sealing off water-producing segments of gravel packed wells. In the method of U.S. Pat. No. 4,972,906, an epoxy resin composition is placed in the gravel packing liner at a spot above the location where water entry is occurring. The epoxy resin flows through the slotted and/or screened liner and into the gravel pack. A sufficient amount of epoxy resin composition is preferably deposited in the well liner to fill and plug the gravel pack up to a point above the uppermost point of water entry.
U.S. Pat. No. 5,086,850 discloses a method for terminating water flow through a gravel pack contained in a vertical well. The method of U.S. Pat. No. 5,086,850 utilizes a cement slurry wherein the diameters of the cement particles contained in the slurry are not greater than about 30 microns. As with the method of U.S. Pat. No. 4,972,906, the method of U.S. Pat. No. 5,086,850 operates to plug off the entire lowermost portion of the vertical well. In the method of U.S. Pat. No. 5,086,850, a sufficient amount of cement slurry is placed in the gravel packing liner to saturate the portion of the gravel pack through which water production is occurring. A sufficient pressure is then applied against the slurry to force the slurry into the gravel pack and at least partially into the subterranean formation from which the water is being produced. Hydraulic pressure is maintained against the slurry for a time sufficient to ensure that the slurry remains in and hardens in the gravel pack.
As is apparent, neither U.S. Pat. No. 4,972,906 nor U.S. Pat. No. 5,086,850 provides a method wherein a casing liner or other conduit is secured and supported in a horizontal or other highly deviated wellbore. Additionally, these patent disclosures do not provide methods whereby multiple production zones in either a vertical or highly deviated lateral can be effectively separated and isolated.
Thus, a need presently exists for a reliable completion method which: (a) can be effectively used in horizontal and other highly deviated wellbores; (b) will not substantially reduce the production rates obtainable from naturally producing formations; (c) will provide a desirable degree of casing support; and (d) will allow individual zones of interest to be quickly and effectively isolated and/or opened.